Failure detecting system

ABSTRACT

The present invention relates to a failure detecting system that enables the detection of a break in a rail and the like by a simple network configuration. Detecting units ( 20  and  50 ), relay units ( 30 A,  30 B,  60 A through  60 C) and terminal units ( 40  and  70 ) are arranged along rails ( 11, 11 A and  11 B). Using the rails ( 11, 11 A and  11 B) as transmission media, ultrasonic waves transmitted from the detecting units ( 20  and  50 ) are transmitted to the terminal units ( 40  and  70 ) by the relay units ( 30 A,  30 B,  60 A through  60 C), and when the terminal units ( 40  and  70 ) receive the ultrasonic waves, the ultrasonic waves are returned from the terminal units ( 40  and  70 ), relayed by the relay units ( 30 A,  30 B,  60 A through  60 C), and transmitted to the detecting units ( 20  and  50 ). Thus, it is judged whether there is a break in the rails ( 11, 11 A and  11 B), based on the ultrasonic wave reception state in the detecting units ( 20  and  50 ).

This application is a continuation of PCT/JP00/08549 filed on Dec. 1,2000.

TECHNICAL FIELD

The present invention relates to a failure detecting system fordetecting failures such as breaks and the like in rails or pipes laidover long distances by using sound wave. In particular, the presentinvention relates to a technique for achieving simplification of such asystem.

BACKGROUND ART

For example, in the field of railway signalling, a detection of train isperformed by using track circuits. However, as a secondary function,these track circuits are provided with rail failure detecting functionsfor detecting whether there is a break in the rails.

Incidentally, in recent years, train detecting systems using radiotransmission for the purpose of facilitation of safety have beenconsidered. In the case where a train detecting system using radiotransmission is adopted, since this system does not have a function fordetecting rail breaks, it is necessary to provide separately a facilityfor detecting rail failures such as breaks and the like. An advantage ofa train detecting system using radio transmission is that signal linecabling is not required. Accordingly, it is desirable for a rail failuredetecting apparatus used together with a train detecting system usingradio transmission to be one that does not require the signal linecabling.

For such a rail failure detecting system, systems using ultrasonic wavesare well known (refer to International Publication WO98/7610 and U.S.Pat. 5,743,495).

FIG. 1 shows an example of a conventional break detecting system fordetecting rail breaks over a long distance using ultrasonic waves.

In FIG. 1, a large number of terminal devices 2 ₁, 2 ₂, 2 ₃, . . . areinstalled at intervals along a rail 1. The terminal devices 2 ₁, 2 ₂, 2₃, . . . are provided with ultrasonic wave transmitter-receivers 3 ₁, 3₂, 3 ₃, . . . and communication units 4 ₁, 4 ₂, 4 ₃, . . . respectively,and are connected to a central processing unit 5 via a communicationline 6 so as to be able to communicate with the central processing unit5.

In this conventional system, ultrasonic waves are transmitted from eachterminal device to the next terminal device such that the terminaldevice 2 ₁ transmits ultrasonic waves to the next terminal device 2 ₂,the terminal device 2 ₂ transmits ultrasonic waves to the next terminaldevice 2 ₃, and the terminal device 2 ₃ transmits ultrasonic waves tothe next terminal device. Each of the terminal devices 2 ₁, 2 ₂, 2 ₃, .. . periodically informs the central processing unit 5, through each ofthe communication units 4 ₁, 4 ₂, 4 ₃, . . . , whether ultrasonic waveshave been transmitted or received.

For example, if a rail break occurs between the terminal device 2 ₁ andthe terminal device 2 ₂, an ultrasonic wave signal transmitted from theterminal device 2 ₁ is not received by the terminal device 2 ₂. If thereis no information from the terminal device 2 ₂ to the central processingunit 5 that the signal has been received, then the central processingunit 5 judges that there is a break in the rail between the terminaldevice 2, and the terminal device 2 ₂.

Furthermore, in the case where the location of a rail break is detectedby the system in FIG. 1, when each of the terminal devices 2 ₁, 2 ₂, 2₃, . . . receives reflected waves, it immediately informs the centralprocessing unit 5 that reflected waves have been received. The centralprocessing unit 5 can calculate the location where reflection occurred,that is, the location of a break in the rail, based on the time theultrasonic waves were transmitted and the time the reflected waves werereceived.

Incidentally, the transmission distance of ultrasonic waves depends onthe form and installation condition of an ultrasonic transmissionmedium. For example, in the case of a pipe, equipments for fitting pipeincrease the attenuation of ultrasonic waves. Furthermore, in the caseof a rail, the attenuation of ultrasonic waves becomes large by sleeperand rail fastenings. Generally, the detection range in the case of pipefailure detection using reflection of ultrasonic waves is approximatelyfew score meters, and the detection range in the case of rail breakdetection is from 1 to 2 km.

Therefore, in the case of detecting breaks in a rail or pipe installedover a long distance, in the conventional system in FIG. 1, if thenumber of terminal devices connected to the central processing unit viathe communication line is increased, there is a problem in that controlof the network comprising terminal devices, communication lines and acentral processing unit becomes complicated.

A method has also been reported for performing long distancetransmission by generating powerful ultrasonic waves. However, sincethere are possibilities of the ultrasonic wave generating apparatusbecoming too big, and the ultrasonic transmission medium itself gettingdamaged, it is difficult to utilize such a method for detecting breaksin pipes and rails.

The present invention takes such conventional problems intoconsideration, and has an object of providing a failure detecting systemcapable of reducing the number of terminal devices connected to acommunication line of a network, and also simplifying the network.

DISCLOSURE OF THE INVENTION

In order to achieve the above object, the construction of a failuredetecting system of the present invention is such that a detecting unit,relay units and a terminal unit are arranged along a detection object atintervals, sound wave transmitted from the detecting unit is relayed bythe relay units to be transmitted to the terminal unit using thedetection object as a transmission medium, and when the terminal unitreceives the transmitted sound wave, the sound wave is returned from theterminal unit, and relayed by the relay units to be transmitted to thedetecting unit, so that it is judged whether or not there is a failurein the detection object, based on the sound wave reception state in thedetecting unit.

According to such a construction, the sound wave reception state may bemonitored in the detecting unit, and even in the case where failuressuch as breaks and the like in a detection object are detected over along distance, only the detecting unit need be connected to a centralprocessing unit or the like via a communication line. Therefore, it ispossible to simplify the communication network.

Furthermore, each of the relay unit is provided with a firsttransmission and reception section that transmits and receives soundwave on the detecting unit side, and a second transmission and receptionsection that transmits and receives sound wave on the terminal unitside, wherein when the first transmission and reception section receivessound wave from the detecting unit side, the second transmission andreception section transmits the sound wave to the terminal unit side,and when the second transmission and reception section receives thesound wave from the terminal unit side, the first transmission andreception section transmits the sound wave to the detecting unit side.If the construction is such that when the relay unit receives sound wavefrom the detecting unit side, the first transmission and receptionsection returns the sound wave to the detecting unit side, then in acase where there is no failure in the detection object, since receptionsignals corresponding to the number of installed relay units andterminal unit are received, it is possible to monitor the operatingstates of the relay units and the terminal unit. Moreover, whenreflected sound wave is received from a failure, since a location offailure can be specified based on the time from the reception signalimmediately beforehand to the reception signal by the reflected soundwave, it is possible to suppress errors in detecting the location offailure caused by a difference in timing from receiving to transmittingin the relay unit, and hence the location of failure can be specifiedaccurately. Furthermore, in the detecting unit, it is possible tocorrect a change in sound wave propagation speed caused by theinstallation environment and the like, based on the time from when thedetecting unit transmits sound wave to when it receives the sound wavetransmitted to the direction of the detecting unit by the adjacent relayunit that received the sound wave, and hence the location of failure canbe specified accurately.

If the sound wave transmission levels of the relay unit and the terminalunit are set to be almost the same as the reflected sound wave level inthe vicinity of where these units are arranged, then it is possible tocheck whether the detecting unit and the relay unit maintain the abilityto receive reflected sound wave, respectively.

Furthermore, the construction may be such that the relay unit comprisesat least a transmission and reception section that transmits andreceives sound wave in the directions of both the detecting unit sideand the terminal unit side.

In such a construction, it is becomes possible to easily install atransmission and reception section for a detection object.

In this case, the relay unit is constructed to transmit sound wave witha preset time delay after received the sound wave. If the constructionis such that the time delay is different between when sound wave isreceived for the first time and when sound wave is received for a secondor later time, it is possible to differ the transmission timing of eachrelay unit from each other, so that interference due to received soundwave can be avoided.

Furthermore, the construction may be such that when the relay unitreceives a sound wave signal from the terminal unit, it transmits thesame signal as the sound wave signal returned from the terminal unit,and after transmission, the relay of the signal is stopped.

In such a construction, it is possible to avoid unnecessary transmissionof sound wave.

Moreover, the construction may be such that when the relay unit receivesreflected sound wave from a failure in a detection object, it transmitsa signal indicating reception of the reflected sound wave, which isdifferent from any of a sound wave signal transmitted from the detectingunit and a sound wave signal returned from the terminal unit.

Furthermore, the construction may be such that the transmission andreception sections of each the detecting unit, the relay unit and theterminal unit are installed on at least a pair of detection objects thatare separated acoustically from each other, a sound wave signaltransmitted from the detecting unit is transmitted to each of the pairof detection objects alternately to be relayed to the terminal unit viathe relay unit, returned sound wave from the terminal unit aretransmitted to each of the pair of detection objects alternately to besent to the detecting unit via the relay unit, and also a sound wavesignal is transmitted from the detecting unit to each of the pair ofdetection objects alternately.

According to such a construction, by propagating sound wave to each ofthe pair of detection objects alternately, it is possible to propagatesound wave bypassing a break, and it is possible to receive reflectedsound wave from the break with certainty, regardless of a location ofbreak, so that it is possible to specify the location of break even in acase where respective units are arranged at maximum intervals betweenwhich signals can be transmitted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an example of a conventional failuredetecting system.

FIG. 2 is a block diagram showing a first embodiment of the presentinvention.

FIG. 3 shows a configuration example of a relay unit.

FIG. 4 is an operation time chart at a time of normal operation, in thefirst embodiment.

FIG. 5 is an operation time chart for when there is a break, in thefirst embodiment.

FIG. 6 shows the installation state of each unit when there is a jointin a rail.

FIG. 7 shows the installation state of each unit when breaks in a pairof rails are checked at the same time.

FIG. 8 is an operation time chart at a time of normal operation, in asecond embodiment of the present invention.

FIG. 9 is an operation time chart for when there is a break, in thesecond embodiment.

FIG. 10 is an explanatory diagram of the principle of a reflected soundwave reception function checking of a unit.

FIG. 11 shows a third embodiment of the present invention, and is ablock diagram of a case where sound wave is propagated in bi-directions.

FIG. 12 shows a configuration example of a relay unit in the thirdembodiment.

FIG. 13 is an operation time chart at a time of normal operation, in thethird embodiment.

FIG. 14 is a block diagram of a fourth embodiment of the presentinvention.

FIG. 15 is an operation time chart at a time of normal operation, in thefourth embodiment.

FIG. 16 is an operation time chart for when there is a break, in thefourth embodiment.

FIG. 17 is an operation time chart for when there is a break, in a fifthembodiment of the present invention.

FIG. 18 is a diagram for explaining the relationship between sound wavetransmission distance and reflected wave reception range in a case whererespective units are arranged at maximum intervals between which signalscan be transmitted.

FIG. 19 is a block diagram of a sixth embodiment of the presentinvention.

FIG. 20A and FIG. 20B are explanatory diagrams of signal propagationoperation, in the sixth embodiment.

FIG. 21 is a time chart at a time of signal propagation operation inFIG. 20A.

FIG. 22 is a time chart at a time of signal propagation operation inFIG. 20B.

FIG. 23A and FIG. 23B are explanatory diagrams showing an example ofsignal propagation operation when there is a break, in the sixthembodiment.

FIG. 24 is a time chart at a time of signal propagation operation inFIG. 23A.

FIG. 25 is a time chart at a time of signal propagation operation inFIG. 23B.

BEST MODE FOR CARRYING OUT THE INVENTION

As follows is a description of preferred embodiments of a failuredetecting system according to the present invention, with reference todrawings.

FIG. 2 shows a first embodiment of the present invention, and shows anexample applied to a rail break detection.

In FIG. 2, along a break detection region of a rail 11, being adetection object, a detecting unit 20 is arranged at the start of thedetection region and a terminal unit 40 is arranged at the end of thedetection region. Furthermore, an appropriate number of relay units 30Aand 30B (the present embodiment shows an example with two unitsarranged) is arranged at intervals in accordance with the length of thedetection region. Here, needless to say, the number of relay units isnot limited to two.

The detecting unit 20 is provided with an ultrasonic transducer 21attached in contact with the rail 11, being a transmission medium, so asto be enable to transmit ultrasonic waves as sound wave to the directionof relay unit 30A, and to receive ultrasonic waves from the direction ofrelay unit 30A. Furthermore, based on transmission and receptioninformation from transmitting and receiving circuits connected to theultrasonic transducer 21 as described later, the detecting unit 20judges whether or not there is a break, specifies the location of thebreak or the like, and transmits information of the judgment orspecifying result to a central processing unit or the like (not shown inthe figure) via a communication line.

The terminal unit 40 is provided with an ultrasonic transducer 41attached in contact with the rail 11, so as to enable to transmitultrasonic waves to the direction of relay unit 30B, and to receiveultrasonic waves from the direction of relay unit 30B. The ultrasonictransducer 41 is connected to internal transmitting and receivingcircuits, which are not shown in the figure. The construction of theterminal unit 40 is such that when receiving ultrasonic wavestransmitted by the relay unit 30B, it returns the ultrasonic waves tothe relay unit 30B.

The relay units 30A and 30B each is provided with an ultrasonictransducer 31 a, being a first transmission and reception section,attached in contact with the rail 11, so as to enable to transmitultrasonic waves to a direction of detecting unit 20 and to receiveultrasonic waves from the direction of detecting unit 20, and anultrasonic transducer 31 b, being a second transmission and receptionsection, attached in contact with the rail 11, so as to enable totransmit ultrasonic waves to the direction of relay unit 30B (terminalunit direction) and to receive ultrasonic waves from the direction ofthe relay unit 30B (terminal unit direction). The construction of therelay unit 30A is such that when receiving ultrasonic waves transmittedby the detecting unit 20 at the ultrasonic transducer 31 a, it transmitsthe ultrasonic waves to the relay unit 30B via the ultrasonic transducer31 b, and when receiving ultrasonic waves transmitted by the relay unit30B at the ultrasonic transducer 31 b, it transmits the ultrasonic wavesto the detecting unit 20 via the ultrasonic transducer 31 a. The relayunit 30B is constructed similarly. When receiving ultrasonic wavestransmitted by the relay unit 30A at the ultrasonic transducer 31 a, therelay unit 30B transmits the ultrasonic waves to the terminal unit 40via the ultrasonic transducer 31 b, and when receiving ultrasonic wavestransmitted by the terminal unit 40 at the ultrasonic transducer 31 b,it transmits the ultrasonic waves to the relay unit 30A via theultrasonic transducer 31 a.

FIG. 3 shows a configuration example of the relay unit 30A. The relayunit 30B has the same construction, and its description is thus omitted.

In FIG. 3, the relay unit 30A comprises a receiving circuit 33A and atransmitting circuit 33B that can be connected selectively to theultrasonic transducer 31 a via a change-over switch 32, a receivingcircuit 35A and a transmitting circuit 35B that can be connectedselectively to the ultrasonic transducer 31 b via a change-over switch34, and control circuits 36 and 37 that switching control thechange-over switches 32 and 34, respectively, based on informationindicative of the signal reception from the receiving circuits 35A and33A.

Next is a description of operation of the first embodiment withreference to time charts in FIG. 4 and FIG. 5. FIG. 4 shows a time chartfor a case where the rail is normal, and FIG. 5 is a time chart for acase where there is a break between the relay unit 30A and the relayunit 30B.

Firstly, there will be described the operation during normal status,where there is no break in the rail 11.

The detecting unit 20 transmits ultrasonic waves to the direction of therelay unit 30A at a predetermined period. A signal S1 transmitted fromthe detecting unit 20 is received by the ultrasonic transducer 31 a ofthe relay unit 30A, and a reception signal R1 is generated. When thereceiving circuit 33A receives the signal R1, the relay unit 30A outputsinformation indicative of the signal reception to the control circuit37. Based on the information indicative of the signal reception, thecontrol circuit 37 switches the change-over switch 34 to thetransmitting circuit 35B side. In this manner, ultrasonic waves aretransmitted to the relay unit 30B via the ultrasonic transducer 31 b.Accordingly, the transmission signal S1 from the detecting unit 20 isrelayed as a signal S2 by the relay unit 30A, to be transmitted to thedirection of the relay unit 30B. Similarly, the transmission signal S2from the relay unit 30A is received by the ultrasonic transducer 31 a ofthe relay unit 30B, and a reception signal R2 is generated. Thereception signal R2 is relayed as a transmission signal S3 by the relayunit 30B, to be transmitted to the terminal unit 40. The terminal unit40 receives the signal S3, generates a transmission signal S4 due to thegeneration of a reception signal R3, to send the transmission signal S4to the direction of the relay unit 30B. The transmission signal S4 isreceived by the relay unit 30B, and relayed as a transmission signal S5due to the generation of a reception signal R4. The signal S5 isreceived by the relay unit 30A, and relayed as a transmission signal S6due to the generation of a reception signal R5. The signal S6 isreceived by the detecting unit 20, and a reception signal R6 isgenerated.

In this manner, if there is no break in the rail 11, the signal S1transmitted from the detecting unit 20 is relayed by the relay units 30Aand 30B, to be transmitted to the terminal unit 40. An ultrasonic wavesignal returned as information indicative of the signal reception fromthe terminal unit 40 is transmitted to the detecting unit 20 via therelay units 30A and 30B, so that the reception signal R6 is generated inthe detecting unit 20. Since it is possible to calculate in advance thetime for the ultrasonic wave signal to go forth and back between thedetecting unit 20 and the terminal unit 40 via the rail 11, it ispossible to set in advance the generation time of the reception signalR6 in the detecting unit 20 when the rail 11 is normal. Accordingly, bysetting a time range in advance based on a predicted generation time inthe detecting unit 20, and by monitoring whether or not the receptionsignal R6 is generated within the preset time range, it is possible tomonitor whether or not there is a break, and hence if the signal R6 isgenerated within the set time range, the rail 11 can be judged to benormal.

Next is a description of the case where the rail 11 has a break withreference to the time chart in FIG. 5.

In the case where there is a break in the rail 11 between the relayunits 30A and 30B, the transmission signal S2 from the relay unit 30A,based on the transmission signal S1 from the detecting unit 20, isreflected at the break. As a result, the relay unit 30A receivesreflected waves from the break at the ultrasonic transducer 31 b, and areflected reception signal “a” is generated as shown in FIG. 5. When thesignal “a” is generated, the relay unit 30A transmits a signal “b” tothe detecting unit 20 via the ultrasonic transducer 31 a by operationsof the receiving circuit 35A, the control circuit 36 and the change-overswitch 32. The detecting unit 20 generates a reception signal “c” onreceiving the signal “b”. The reception signal “c” which is based on thereflection from the break, becomes outside the set time range earlierthan the generation time of the reception signal R6 (shown by dashedlines in FIG. 5). Hence, it is possible to judge that the receptionsignal “c” is generated by reflected waves from the break.

In the case where it is judged that the reception signal “c” is the onebased on the break, in the detecting unit 20, it is possible tocalculate a rail break location X from the equation X=C·T/2 where T isthe time from the transmission of the signal S1 to the reception ofsignal “c” and C is the propagation speed of ultrasonic waves. Hence, itis possible to specify the break location. Information such as theabovementioned judgment of normal operation and the break location istransmitted to the central processing unit connected to the detectingunit 20 through the communication line, although not shown in thefigure.

As above, in the first embodiment, it is monitored whether or not thereception signal R6 is generated due to a return signal from theterminal unit 40. If the signal R6 is generated, it is judged that therail 11 is normal, and if the reception signal “c” is generated, it isjudged that there is a break. Furthermore, if the detecting unit 20 doesnot receive a signal, it means that some abnormality has occurred in theultrasonic wave transmission system.

In a case where there is a joint in the middle of the detection regionof the rail 11, as shown in FIG. 6, the two ultrasonic transducers ofthe relay unit 30 may be installed on the rail 11 so as to cross over ajoint 11 a. If there is the joint 11 a in the detection region, there isa reflected wave from the joint 11 a. However, if the reception signalR6 is generated based on the transmission from the terminal unit 40, itis judged that the rail is normal.

Furthermore, in a case where breaks in a pair of rails 11 are monitoredat the same time, then as shown in FIG. 7, the detecting unit 20 may bearranged on one of the rails and the terminal unit 40 may be arranged onthe other rail, at one end of the detection region of the rails 11, andalso the relay unit 30 may be arranged at the other end of the detectionregion so that the two ultrasonic transducers are installed across bothrails.

Here, in the case where the constructions are as in FIG. 6 and FIG. 7,the transmission operation of ultrasonic wave signals is similar to thecase in FIG. 2. Therefore, the description is omitted.

In the case of the first embodiment described above, when the number ofrelay units 30 is increased, the cumulative time of a time delay fromthe reception of signal to the transmission of signal in each relay unit30 is increased, and hence the error in the reception time of thereflected signal “c” from the break is increased. Therefore, there is apossibility that the accuracy of detecting the location of a break isreduced.

Next is a description of a second embodiment of the present inventionthat can detect the location of a break accurately regardless of thenumber of relay units.

When a signal is received from the direction of detecting unit, eachrelay unit of the present embodiment relays and transmits the signal tothe direction of terminal unit, and also transmits it back to thedirection of detecting unit via an ultrasonic transducer 31 a. In thiscase, the construction may be such that each relay unit also outputsinformation indicative of the signal reception from the receivingcircuit 33A to the control circuit 36, as shown by the broken line inFIG. 3. The constructions of the detecting unit and the terminal unitare similar to the first embodiment.

Next is a description of operations of the second embodiment withreference to operation time charts in FIG. 8 and FIG. 9. The descriptionhereunder assumes that the detecting unit, relay unit and terminal unitare arranged similarly to those in the first embodiment as shown in FIG.2. In the figures, the same symbols are used for the same items as inFIG. 4 and FIG. 5.

FIG. 8 is an operation time chart in a normal case where there is nobreak in the rail 11. In FIG. 8, on receiving a signal S1, the relayunit 30A generates a reception signal R1 and transmits ultrasonic wavesto the relay unit 30B as a signal S2, similarly to the first embodiment,and at the same time also, as shown in the figure, transmits it as asignal S1′ to the detecting unit 20. On receiving the signal S2, therelay unit 30B generates a reception signal R2 and transmits ultrasonicwaves to the terminal unit 40 as a signal S3, and at the same time, asshown in the figure, transmits it as a signal S1″ to the relay unit 30A.On receiving the signal S1″, the relay unit 30A generates a signal R1″,and transmits it to the detecting unit 20 as a signal S2″. In the casewhere the rail 11 is normal, as shown in the figure, the detecting unit20 generates reception signals R1′ and R2′ based on the transmissionsignals S1′ and S1″ from the relay units 30A and 30B, and the receptionsignal R6 based on the transmission signal S4 from the terminal unit 40,similarly to the first embodiment. Accordingly, if the reception signalR6 is generated within a set time range, the detecting unit 20 can judgethat the rail is normal.

Next is a description of a case where the rail has a break using thetime chart in FIG. 9.

In the case where there is a break between the relay units 30A and 30Bin the rail 11, the relay unit 30A generates normally the transmissionsignals S2 and S1′ similarly to FIG. 8 due to the generation of thereception signal R1, and the reception signal R1′ is generated in thedetecting unit 20. The transmission signal S2 of the relay unit 30A isreflected by the break, a signal “b” is transmitted from the relay unit30A to the detecting unit 20 based on a reflected reception signal “a”,and the detecting unit 20 generates a reception signal “c” based on thereflected waves earlier than the time when the reception signal R2″ isgenerated at normal times. In the present embodiment, in this case, timeT when the signal “c” is received is measured with the time when thereception signal R1′ is generated as a reference, and the location ofthe break in the rail is calculated from this time T and the propagationspeed C. In this manner, it is possible to eliminate an influence ofdelay time between the reception of signal and the transmission ofsignal in each relay unit 30, and also it is possible to specify thelocation of a break more accurately than in the first embodiment.

Furthermore, in the second embodiment, it is possible to compensate fora propagation speed C of ultrasonic waves using the transmission signalS1′ of the relay unit 30A.

That is to say, if a distance between the detecting unit 20 and therelay unit 30A is L, then the time “to” from when the signal S1 isgenerated by the detecting unit 20 to when the reception signal R1′ isgenerated is represented by “to”=2L/C+tx. Here, “tx” represents a timedelay from when the relay unit 30A receives ultrasonic waves to when ittransmits them, which is a fixed value, being fixed by the design. Ifthe time “to” is measured in accordance with the above-describedequation, the propagation speed C at that time can be calculated. Inthis manner, since it is possible to correct the propagation speed C ofthe ultrasonic waves, if the corrected propagation speed C is used fordetecting the location of a break, it is possible to specify thelocation of a break more accurately.

Furthermore, in the case of the second embodiment, as shown in the timechart of FIG. 8, since the reception signals corresponding to the numberof relay units between the detecting unit and terminal unit aregenerated in the detecting unit 20, then by counting the number ofgenerated reception signals, the number of relay units installed can bemonitored sequentially on the side of the detecting unit 20. Therefore,by checking the number of signals to be received and the reception timeson the side of the detecting unit 20, it is possible to monitor theoperating status of all of the relay units 30 and the terminal unit 40.

Moreover, in the construction of the second embodiment, if there is abreak in the rail, the detecting unit does not receive transmissionsignals from the relay units and the terminal unit positioned behind thebreak. Therefore, by monitoring the number of reception signals in thedetecting unit 20, it is possible to detect whether or not there is abreak and the approximate location of the break.

In the case where there is a break between the last relay unit and theterminal unit, it is not possible to detect whether there is a breakfrom the number of reception signals. In this case, it may be judgedwhether the reception signal is caused by the reflection wave at thebreak based on the time that the final reception signal was generated oris caused by the return signal from the terminal unit.

Furthermore, in the construction of the present invention, by settingthe levels of the ultrasonic wave transmissions in the direction ofdetecting unit of each relay unit 30 and the terminal unit 40appropriately, it is possible to monitor whether or not the functionsfor receiving reflected waves from the break are normal in the detectingunit 20 and the relay units 30.

Such a monitoring function will be described in FIG. 10 using thetransmitting and receiving operation between the detecting unit 20 andthe relay unit 30A as an example.

It is assumed that a distance between the detecting unit 20 and therelay unit 30A is Lx. A transmission signal from the detecting unit 20is attenuated before it reaches the location of the relay unit 30A,which is the distance Lx away, and after reached, it is furtherpropagated the distance Lx while being attenuated, to be received by thedetecting unit 20. Therefore, the reception ability of the detectingunit 20 is set so as to enable to detect reflected waves generated atthe maximum distance Lx, that is, the location of the relay unit 30A. Tocheck whether or not the detecting unit 20 has an ability to receivereflected waves generated at the location of the relay unit 30A, thearrangement may be such that, as shown in FIG. 10, the transmissionlevel from the relay unit 30A to the detecting unit 20 is sufficientlylower than the transmission level of the detecting unit 20, in thedirection of relay unit 30A, that is, almost the same level as thereflected waves at the location of the relay unit 30A. Here, to checkthe reflected wave reception function of the other relay units, thelevel of transmissions to the direction of detecting unit in theadjacent relay unit and the terminal unit may be set similarly.

In this manner, it is possible to monitor whether or not the reflectedwave reception functions in the detecting unit 20 and the relay unit 30are normal, at the same time as the break detection operation, and hencethe reliability of the failure detecting system is improved.

Each of the above-described embodiments shows a configuration example inwhich sound wave is propagated to be relayed through the transmissionmedium in one direction from the detecting unit side to the terminalunit side, and alternatively from the terminal unit side to thedetecting unit side. As follows is a description of a configurationexample for a case where sound wave is propagated in bi-directionsthrough the transmission medium.

FIG. 11 shows a third embodiment of the present invention in which soundwave is propagated in bi-directions through the transmission medium.

In FIG. 11, a detecting unit 50, relay units 60A and 60B, and a terminalunit 70, which are arranged along a break detection region of the rail11, being the transmission medium, have ultrasonic transducers 51, 61and 71, respectively, as their transmission and reception sections. Theultrasonic transducers 51, 61 and 71 of the units 50, 60 and 70 aremounted, respectively, such that the ultrasonic wave transmission andreception faces thereof are almost at right angles to the propagationdirection of the rail 11, being the transmission medium. In this manner,ultrasonic waves as sound wave, transmitted from each of the ultrasonictransducers 51, 61 and 71, are propagated in bi-directions through therail 11, the right and left directions in the figure.

The detecting unit 50, which has the same construction as the detectingunit 20, judges whether or not there is a break, specifies the locationof the break or the like, based on transmission and receptioninformation of the ultrasonic waves, and transmits information of theresult to a central processing unit or the like (not shown in thefigure) via a communication line.

The terminal unit 70 is constructed to, when receiving a transmissionsignal from the relay unit 60B, transmit an ultrasonic wave signal thatis different from the transmission signal from the detecting unit 50 inorder to distinguish it from the transmission signal from the detectingunit 50. A different signal means a signal whose generation time isdifferentiated by varying the number of pulses for example. Furthermore,The terminal unit 70 stops relay operation after the transmission, thatis to say, does not perform an operation in which a signal istransmitted whenever received.

The relay units 60A and 60B have the same construction, and have, asshown in FIG. 12, a receiving circuit 63 and a transmitting circuit 64,which can be selectively connected to the ultrasonic transducer 61 via achange-over switch 62, and a control circuit 65, which switchingcontrols the change-over switch 62 based on information that a signalhas been received from the receiving circuit 63 and information of thereception signal form, and also controls the transmission mode of thetransmitting circuit 64.

That is to say, in each of the relay units 60A and 60B, when a signal isreceived, the change-over switch 62 is switched to the transmittingcircuit 64 side by the control circuit 65 to transmit a signal, andthereafter is returned to the receiving circuit 63 side. Then, if thereceived signal is a signal from the detecting unit 50, a signalidentical to the signal from the detecting unit 50 is transmitted, whileif the received signal is a signal from the terminal unit 70, a signalidentical to the signal from the terminal unit 70 is transmitted. Aftertransmitting the signal identical to the signal from the terminal unit70, the relay operation is stopped, and the transmission operation isnot performed even if a signal is received.

A signal relay operation in the third embodiment will be described withreference to a time chart in FIG. 13. Here, the white squares in thefigure indicate signals identical to those from the detecting unit 50,and the black squares indicate signals identical to those from theterminal unit 70.

The detecting unit 50 transmits an ultrasonic wave signal S1 in apredetermined cycle. A reception signal R1 is generated in the relayunit 60A due to the signal S1, and the relay unit 60A transmits a signalS2 identical to the signal S1. Since the signal S2 is propagated inbi-directions through the rail 11, reception signals R′ and R2 aregenerated in the detecting unit 50 and the relay unit 60B, respectively,as shown in the figure. The relay unit 60B transmits a transmissionsignal S3 in response to the generation of the reception signal R2, andreception signals R2′ and R3 are generated in the relay unit 60A and theterminal unit 70, respectively. Since the relay unit 60A transmits atransmission signal S2′ in response to the generation of the receptionsignal R2′, a reception signal R2″ is generated in the detecting unit50, and a reception signal R3′ is generated in the relay unit 60B.Furthermore, the terminal unit 70 transmits a signal S4, which isdifferent, for example in pulse numbers, from the signal S1 from thedetecting unit 50, in response to the generation of the signal R3, and areception signal R4 is generated in the relay unit 60B in response tothis signal S4. The relay unit 60B transmits a signal S5 in response tothe generation of the reception signal R4. The relay unit 60A transmitsa signal S6 in response to the generation of the reception signal R5 dueto the signal S5, and a reception signal R6 is generated in thedetecting unit 50.

Here, since the terminal unit 70 stops the relay operation aftertransmitting the signal S4, then even if a reception signal R4′ isgenerated due to the signal S5 from the relay unit 60B, it does notperform the transmission operation. Similarly, since the relay unit 60Balso stops the relay operation after transmitting the signal S5 due tothe signal S4 from the terminal unit 70, even if a reception signal R5′is generated by receiving the signal S6, it does not perform thetransmission operation.

In this third embodiment, if the reception signal R6 is generated withina predetermined time range, the detecting unit 50 judges that the rail11 is normal. In the case where there is a break in the rail 11, it ispossible to detect the break similarly to the second embodiment as shownin FIG. 9. Furthermore, similarly to the second embodiment, since thesame number of reception signals is generated in the detecting unit 50as the number of relay units between the detecting unit and terminalunit, by counting the number of reception signals generated, the numberof relay units installed can be sequentially monitored in the detectingunit 50. Therefore, by checking the number of reception signals and thereception times, it is possible to monitor the operating status of therelay units 60A and 60B and the terminal unit 70. It is easier to mountultrasonic transducers on the transmission medium compared with theconstruction in which ultrasonic waves are propagated and relayed in asingle direction through the transmission medium, and hence there is anadvantage that there is no restriction in the mounting.

Incidentally, in the case of the third embodiment, as shown in FIG. 13,the transmission timing of the signal S4 from the terminal unit 70 andthe transmission timing of the signal S2′ from the relay unit 60Aoverlap with each other, so there is a possibility that the receptionsignals R4 and R3′ interfere with each other in the relay unit 60B.

Next is a description of a fourth embodiment of the present invention,wherein the problem of reception signal interference as described aboveis avoided.

In the fourth embodiment, the transmission operation after receiving asignal is delayed in the relay operation of each relay unit, and a delaytime is changed. To be specific, the construction is such that the delaytime from when the relay unit receives a signal to when it transmits asignal is different between the first time it receives a signal and thesecond or later time it receives a signal. Furthermore, each relay unithas a construction to transmit a signal identical to a signal from theterminal unit when receiving reflected waves from a break.

A signal transmission operation in the fourth embodiment will bedescribed with respect to a case where three relay units 60A, 60B and60C are provided as shown in FIG. 14 with reference to a time chart inFIG. 15. In FIG. 15, T2 designates a delay time of each of the relayunits 60A through 60C when receiving a signal for the first time, and T3designates a delay time when receiving a signal for a second or latertime. T1 designates a signal propagation time between units.

As shown in FIG. 15, each of the relay units 60A through 60C transmits asignal after the lapse of time T2 from when receiving a first receptionsignal, and transmits a signal after the lapse of time T3 from whenreceiving a second or later time reception signal. Furthermore, theterminal unit 70 transmits a signal after the lapse of time T2 from whenreceiving a signal from the relay unit 60C. Relay operations other thanchanging the transmission timing are similar to the case of the thirdembodiment.

In such a construction, when the relay unit 60B receives a signal fromthe relay unit 60A and a signal from the relay unit 60C as shown in Aand C of FIG. 15, and when the relay unit 60C receives a signal from therelay unit 60B and a signal from the terminal unit 70 as shown in B ofFIG. 15, the reception timing of reception signals is delayed, and henceit is possible to prevent reception interference even in the case whereultrasonic waves are propagated in bi-directions.

Next is a description of signal relay operation in the case where thereis a break between the relay units 60B and 60C in the fourth embodiment,based on the time chart in FIG. 16.

In a case where there is a break between the relay units 60B and 60C, asshown by the broken line in FIG. 14, a transmission signal “a” from therelay unit 60B is reflected by the break, and a reception signal “b” isgenerated due to the reflected waves. The relay unit 60B transmits asignal “c” identical to a signal from the terminal unit 70 after thelapse of time T3 from when the reception signal “b” is generated. Inresponse to the generation of this signal “c”, a reception signal “d”based on the reflected waves is generated in the detecting unit 50 bythe relay of the relay unit 60A. In the detecting unit 50, after areception signal a′ is generated based on the transmission signal “a”from the relay unit 60B, the reception signal “d” is generated with adelay of a time (Tr+T3). Here, the time Tr designates a time after thetransmission signal “a” is generated from the relay unit 60B to when thereception signal “b” is generated due to the reflected waves.

Accordingly, in the detecting unit 50, in this case, by calculating thereception time (Tr+T3) of the signal “d” due to the reflected wavesbased on the time when the reception signal a′ is generated, it ispossible to detect that there is a break between the relay units 60B and60C, at a location corresponding to a propagation time Tr/2, ahead ofthe relay unit 60B.

In the fourth embodiment, the construction is such that when receivingreflected waves, each of the relay units 60A through 60C transmits asignal identical to a signal from the terminal unit 70. However, theconstruction may be such that a signal different from the transmissionsignal from the detecting unit 50 and the transmission signal from theterminal unit 70 is transmitted.

FIG. 17 shows a time chart of signal relay operation in a fifthembodiment of the present invention with such a construction. Thelocation of a break is the same as that in FIG. 14. Here, the fifthembodiment has a construction in which a signal is transmittedimmediately after receiving reflected waves.

In FIG. 17, when a reflected wave reception signal “b” is generatedbased on a transmission signal “a”, the relay unit 60B transmits asignal “e” of a kind different from the signal from the terminal unit 70after the lapse of the time T3. On receiving this transmission signal“e”, the relay unit 60A transmits a signal “f” without a delay.Accordingly, in the detecting unit 50, a signal “g” based on the signal“f” from the relay unit 60A is generated with the time delay Tr, afterthe reception signal a′ is generated based on the transmission signal“a” from the relay unit 60B.

In such a construction, the detecting unit 50 can specify the locationof a break by calculating the reception time Tr of the signal “g” due tothe reflected waves based on the time when the reception signal a′ wasgenerated. Therefore, it is not necessary to use time T3, compared withthe case of the fourth embodiment in FIG. 16, and hence the specifyingoperation of the break location becomes simplified.

Incidentally, if each unit is arranged at maximum interval over which asignal can be transmitted, it is possible to reduce the number of relayunits as minimum as possible. That is to say, as shown in FIG. 18, eachof units SA, SB and SC is arranged at the maximum interval L over whicha signal can be transmitted. However, in the case where ultrasonic wavesare transmitted bi-directions of a rail, even if the reflectance of asignal (ultrasonic wave) is assumed to be 100%, the range where each ofthe units SA, SB and SC can receive reflected waves is about half thedistance L between units, that is, a distance range of L/2 from thelocation of each unit. Accordingly, if there is a break in the locationshown by a broken line in the figure, for example, the unit SB cannotreceive reflected waves from the break, and hence although the detectingunit can detect that there is a break because it does not receive areception signal from the terminal unit, it cannot specify the locationof the break.

FIG. 19 shows a sixth embodiment of the present invention, which canspecify the location of a break regardless of the location of the breakusing the unit arrangement configuration as shown in FIG. 18.

The sixth embodiment has a construction in which at least a pair oftransmission media, for example, a pair of rails 11A and 11B, are usedas shown in FIG. 19, and by switching the transmission media throughwhich sound wave is transmitted alternately, a signal is transmitted toa unit that can receive reflected waves from a break, so that thelocation of the break can be specified.

In FIG. 19, the detecting unit 50, the relay units 60A through 60C andthe terminal unit 70 have two ultrasonic transducers each, 51A and 51B,61A and 61B, and 71A and 71B, respectively. One set of ultrasonictransducers 51A, 61A and 71A is installed on the rail 11A side, and theother set of ultrasonic transducers 51B, 61B and 71B is installed on therail 11B side. Furthermore, the constructions of the relay units 60Athrough 60C and the terminal unit 70 are the same as those shown by thesolid lines in FIG. 3. Each ultrasonic transducer transmits ultrasonicwaves when it receives a signal from the other ultrasonic transducer.Here, similar to the fourth embodiment, the signal generating state andthe relay operation of each unit are such that signals generated by thedetecting unit and terminal unit are different from each other. At afirst time of receiving a signal, a signal is transmitted after thelapse of time T2, and at a second or later time of receiving a signal, asignal is transmitted after the lapse of time T3. Moreover, whenreceiving reflected waves from a break, the relay unit transmits asignal indicating that reflected waves have been received.

Signal relay operations of the present embodiment in the case wherethere is no break will be described based on FIG. 20.

In the sixth embodiment, the transmission operations of FIG. 20A andFIG. 20B are executed alternately. That is to say, the signaltransmission operation from the ultrasonic transducer 51A of thedetecting unit 50 is executed as in FIG. 20A, and then the signaltransmission operation from the ultrasonic transducer 51B is executed asin FIG. 20B.

In FIG. 20A, after a transmission signal from the ultrasonic transducer51A side is propagated to the terminal unit 70 in the order of solidline arrows A through D in the figure, a signal from the terminal unit70 is propagated to the detecting unit 50 in the order of broken linearrows E through H in response.

That is to say, the transmission signal from the ultrasonic transducer51A is propagated through the rail 11A as shown by the arrow A, to bereceived by the ultrasonic transducer 61A of the relay unit 60A, and asignal is transmitted to the other rail 11B from the ultrasonictransducer 61B of the relay unit 60A as shown by the arrow B, to bereceived by the ultrasonic transducer 61B of the relay unit 60B. Next, asignal is transmitted from the ultrasonic transducer 61A of the relayunit 60B to the rail 11A as shown by the arrow C, to be received by theultrasonic transducer 61A of the relay unit 60C, and a signal istransmitted from the ultrasonic transducer 61B of the relay unit 60C tothe rail 11B as shown by the arrow D, to be received by the ultrasonictransducer 71B of the terminal unit 70. On receiving the signal, theterminal unit 70 transmits a signal different from the signal from thedetecting unit 50, from the ultrasonic transducer 71B to the rail 11B asshown by the arrow E. This signal is received by the ultrasonictransducer 61B of the relay unit 60C, and a signal is transmitted fromthe ultrasonic transducer 61A to the rail 11A as shown by the arrow F,to be received by the ultrasonic transducer 61A of the relay unit 60B.Next, a signal is transmitted from the ultrasonic transducer 61B of therelay unit 60B to the rail 11B as shown by the arrow G, to be receivedby the ultrasonic transducer 61B of the relay unit 60A. Next, a signalis transmitted from the ultrasonic transducer 61A of the relay unit 60Ato the rail 11A as shown by the arrow H, to be received by theultrasonic transducer 51A of the detecting unit 50. Thus, the signalfrom the terminal unit 70 is transmitted to the detecting unit 50 inresponse. FIG. 21 shows a detailed time chart for the transmitting andreceiving operations of each unit in the case of FIG. 20A.

When the operations in FIG. 20A are completed, the signal transmissionoperations in FIG. 20B are executed. In FIG. 20B, after a transmissionsignal from the ultrasonic transducer 51B side of the detecting unit 50is propagated to the terminal unit 70 in the order of solid line arrowsA′ through to D′ in the figure, a signal is propagated from the terminalunit 70 to the detecting unit 50 in the order of broken line arrows E′through H′ in response. The transmission operations in FIG. 20B and FIG.20A are the same except that the transmitting and receiving order ofeach ultrasonic transducer in each unit is reversed. Therefore, thedescription is omitted. FIG. 22 shows a detailed time chart for thetransmission operations of each unit in the case of FIG. 20B.

Next is a description of the transmission operations in the case wherethere is a break in the vicinity of the relay unit 60C on the rail 11Abetween the relay unit 60B and the relay unit 60C, for example, withreference to FIG. 23 through FIG. 25.

FIG. 23A shows the transmission operations when a signal is transmittedfrom the ultrasonic transducer 51A in FIG. 20A, and FIG. 24 shows adetailed time chart for the transmitting and receiving operations ofeach unit in this case. FIG. 23B shows the transmission operations whena signal is transmitted from the ultrasonic transducer 51B in FIG. 20B,and FIG. 25 shows a detailed time chart of the transmitting andreceiving operations of each unit in this case.

The transmission operations when a signal is transmitted from theultrasonic transducer 51A as shown in FIG. 23A will be described.

Similarly to the case of FIG. 20A, a transmission signal from theultrasonic transducer 51A of the detecting unit 50 is relayed in theorder of solid line arrows A and B in FIG. 23A, to be received by theultrasonic transducer 61B of the relay unit 60B, and a signal istransmitted from the ultrasonic transducer 61A of the relay unit 60B inbi-directions of the rail 11A as shown by a solid line arrow C. However,if there is a break, the signal of the arrow C transmitted from theultrasonic transducer 61A of the relay unit 60B is not propagated to therelay unit 60C since it is reflected by the break. As a result, therelay unit 60C and the terminal unit 70 cannot receive ultrasonic waves,as shown in FIG. 24.

On the other hand, the signal of the arrow C, which has been propagatedfrom the relay unit 60B in the left hand direction in FIG. 23, isreceived by the ultrasonic transducer 61A of the relay unit 60Asimilarly to the case where there is no break, transmitted from theultrasonic transducer 61B of the relay unit 60A to the rail 11B again asshown by a solid line arrow D, to be received by the ultrasonictransducer 51B of the detecting unit 50 and the ultrasonic transducer61B of the relay unit 60B again. In the case where there is no break,since the relay unit 60B receives a signal from the relay unit 60C afterreceiving the signal of the arrow D as shown in FIG. 21, it transmits asignal after the lapse of time T3 from when it receives the signal ofthe arrow D. However, in the case where there is a break, since there isno signal transmitted from the relay unit 60C, when time T3 has elapsedafter receiving the signal of the arrow D as shown in FIG. 24, the relayunit 60B transmits a signal to the rail 11A as shown by a solid linearrow in FIG. 23A. As a result, in the case where there is a break, thesecond transmission timing of the relay unit 60B becomes earlier thanthe case where there is no break. The transmission signal of the arrow Dis received by the relay unit 60A, and transmitted from the relay unit60A to the rail 11B as shown by a solid line arrow F, to be received bythe detecting unit 50. Accordingly, the reception timing of thereception signal based on the second transmission operation of the relayunit 60B in the detecting unit 50 is earlier than the case where thereis no break, and thus the detecting unit 50 detects this earlierreception timing, to judge that there is a break.

When judging that there is a break, the detecting unit 50 transmits acontrol signal (shown by a black square in FIG. 24) to advise the relayunits to stop relay operations. The control signal is transmitted to therelay units 60A and 60B in the order of broken line arrows G, H and I inFIG. 23A. On receiving the control signal, the relay units 60A and 60Bstop relay operations after transmitting similar signals. Afterwards,the detecting unit 50 executes a transmission operation from theultrasonic transducer 51B as shown in FIG. 23B in order to confirmwhether or not the relay operation is normal so that ultrasonic wavescan be propagated to the terminal unit 70.

Similarly to FIG. 20B, the transmission signal from the ultrasonictransducer 51B of the detecting unit 50 is relayed to the relay unit 60Cvia the relay unit 60A and the relay unit 60B in the order of solid linearrows A′ through D′ in FIG. 23B, and the signal is transmitted from theultrasonic transducer 61A of the relay unit 60C in bi-directions of therail 11A as shown by a solid line arrow D′ in the drawing.

The signal of the solid line arrow D′, which has been transmitted fromthe relay unit 60C and propagated in the right hand direction in thefigure, is reflected by the break, and the reflected waves are receivedby the ultrasonic transducer 61A of the relay unit 60C. The relay unit60C that has received the reflected waves, immediately transmits areflected wave reception signal (shown by a symbol A in FIG. 25)indicating that reflected waves have been received, from the ultrasonictransducer 61B to the rail 11B as shown by a broken line arrow F′ in thefigure, and the relay unit 60B that has received this reflected wavereception signal, transmits a similar reflected wave reception signal Aimmediately from the ultrasonic transducer 61A to the other rail 11A asshown by a broken line arrow G′, and the relay unit 60A that hasreceived this, similarly transmits a reflected wave reception signal Aimmediately from the ultrasonic transducer 61B to the rail 11B as shownby a broken line arrow H′, to be received by the detecting unit 50. Thedetecting unit 50 calculates the time (=T2−T3+2T1+Tr) from the receptionof the previous signal to the reception of the reflected wave receptionsignal, and specifies the location of the break.

Here, the signal propagated from the relay unit 60C in the right handdirection in the figure is received by the terminal unit 70, atransmission signal from the terminal unit 70 is propagated to thedetecting unit 50 in the order of the broken line arrows E′ through H′similarly to the case where there is no break as shown in FIG. 22, andrelay operations of the detecting unit 50 and each of the relay units60A through 60C are stopped. Furthermore, by receiving the signal fromthe terminal unit 70, the detecting unit 50 judges that the operation ofeach unit is normal.

As described above, in a construction in which relay units are disposedbetween a detecting unit and a terminal unit, ultrasonic wavestransmitted from the detecting unit are relayed to the terminal unit bythe relay units using a failure detection target section as atransmission medium, and a signal from the terminal unit is transmittedto the detecting unit via the relay units in response, it is possiblefor only the detecting unit to be connected to a central processing unitby a communication line, and hence it is possible to simplify a failuredetecting system network. Furthermore, in a construction in whichultrasonic transducers are installed such that ultrasonic waves arepropagated in bi-directions, the ultrasonic wave transmitting andreceiving faces of the ultrasonic transducers may be simply installed atright angles to the transmission medium. Therefore, installationenvironment restrictions are reduced, and hence the work of installingultrasonic transducers is facilitated.

Moreover, for example, in a wireless communication network in which alarge number of base stations are installed, since electrical powersupplies and communication equipment for network connections areinstalled in the base stations, if detecting units are installed nearthe base stations, it is possible to utilize the existing network foranother purpose, and also the interconnection length of thecommunication lines can be shortened. Accordingly, it is also possibleto use the wireless train detecting system network as described above,it being ideal to use the failure detecting system in common with thewireless train detecting system.

Furthermore, similarly to the conventional system in FIG. 1, in the casewhere the relay units and the terminal unit are also connected to thenetwork in the construction in FIG. 2, failures can be monitored by botha failure detecting system using a network such as the conventionalsystem, and a failure detecting system according to a construction ofthe present invention, in which the detection object is used as aninformation propagation medium. Such a system structure is a multipleredundancy system using physically different devices, and so safety isimproved for failures occurring in either of the two systems.

The applications of the failure detecting system of the presentinvention are not limited to rails, and the system is applicable topipes for fluid transfer, such as pipelines and the like, provided theyare structures constructed over a long distance, through whichultrasonic waves can be propagated.

INDUSTRIAL APPLICABILITY

The present invention can simplify the structure of a failure detectingsystem for rails, pipelines and the like, which are constructed over along distance. Therefore, its industrial applicability is high.

1. A failure detecting system, comprising a detecting unit, relay unitsand a terminal unit arranged along a detection object at intervals, anda sound wave is transmitted from the detecting unit and relayed by therelay units to the terminal unit using said detection object as atransmission medium, wherein said terminal unit receives the transmittedsound wave, the sound wave is returned from said terminal unit, andrelayed by said relay units to said detecting unit, and said detectingunit judges whether or not there is a failure in said detection objectbased on the sound wave reception state in said detecting unit.
 2. Afailure detecting system according to claim 1, wherein said detectingunit judges whether or not there is a failure in said detection object,based on whether or not it has received the sound wave returned fromsaid terminal unit.
 3. A failure detecting system according to claim 2,wherein said detecting unit judges whether or not the sound wavereturned from said terminal unit is received, based on whether or notsaid returned sound wave is received within a predetermined time rangeafter the sound wave is transmitted.
 4. A failure detecting systemaccording to claim 1, wherein each of said relay units is provided witha first transmission and reception section that transmits and receivessound wave on the detecting unit side, and a second transmission andreception section that transmits and receives sound wave on the terminalunit side, and when said first transmission and reception sectionreceives sound wave from the detecting unit side, said secondtransmission and reception section transmits sound wave to the terminalunit side, and when said second transmission and reception sectionreceives sound wave from the terminal unit side, said first transmissionand reception section transmits sound wave to the detecting unit side.5. A failure detecting system according to claim 4, wherein uponreceiving reflected sound wave from a failure of said detection object,said detecting unit specifies the location of said failure based on thetime from when it transmits the sound wave to when it receives saidreflected sound wave.
 6. A failure detecting system according to claim4, wherein upon receiving sound wave from said detecting unit side, saidrelay unit returns the sound wave from said first transmission andreception section to the detecting unit side.
 7. A failure detectingsystem according to claim 6, wherein said detecting unit corrects thetransmission speed of the sound wave, based on the time from when ittransmits the sound wave to when it receives return sound wave from saidfirst transmission and reception section of the adjacent relay unit. 8.A failure detecting system according to claim 4, wherein sound wavetransmission levels of said relay unit and terminal unit are set to bealmost the same as the sound wave reflection levels in the vicinity ofwhere these units are arranged.
 9. A failure detecting system accordingto claim 1, wherein said relay unit comprises at least a transmissionand reception section that transmits and receives sound wave in thedirections of both said detecting unit side and terminal unit side. 10.A failure detecting system according to claim 9, wherein said relay unittransmits a sound wave after the lapse of a preset time delay afterreceiving a sound wave, and said time delay is different between whensound wave is received for the first time and when sound wave isreceived at a second or later time.
 11. A failure detecting systemaccording to claim 9, wherein said terminal unit transmits a sound wavesignal that is different from a sound wave signal transmitted from thedetecting unit.
 12. A failure detecting system according to claim 11,wherein when a received sound wave signal is a sound wave signalreturned from said terminal unit, said relay unit transmits the samesignal as the sound wave signal returned from the terminal unit.
 13. Afailure detecting system according to claim 12, wherein said relay unitstops the relay operation thereof after having transmitted the samesignal as the sound wave signal returned from the terminal unit.
 14. Afailure detecting system according to claim 9, wherein when receivingreflected sound wave from a failure of said detection object, said relayunit relays a signal indicating reception of the reflected sound wave toadvise the detecting unit.
 15. A failure detecting system according toclaim 14, wherein the signal indicating reception of said reflectedsound wave is different from any of a sound wave signal transmitted fromthe detecting unit and a sound wave signal returned from the terminalunit.
 16. A failure detecting system according to claim 9, wherein thetransmission and reception sections of each of said detecting unit,relay unit and terminal unit are installed on at least a pair ofdetection objects that are separated acoustically from each other, asound wave signal transmitted from said detecting unit is transmitted toeach of said pair of detection objects alternately to be relayed to theterminal unit via said relay unit, a sound wave returned from theterminal unit is transmitted to each of the pair of detection objectsalternately to be sent to the detecting unit via the relay unit, andalso a sound wave signal is transmitted from the detecting unit to eachof said pair of detection objects alternately.
 17. A failure detectingsystem according to claim 16, wherein upon judging that the sound wavepropagation state is abnormal, based on the sound wave reception state,said detecting unit transmits a control signal to advise the relay unitsand the terminal unit to stop relay operations.
 18. A failure detectingsystem according to claim 17, wherein after having transmitted saidcontrol signal, said detecting unit transmits a signal to confirm thatthe relay operations of the relay unit and the terminal unit are normal.19. A failure detecting system according to claim 1, wherein saiddetection object is a rail.